Chlamydia, an STI caused by the bacteria Chlamydia trachomatis, is most prevalent in women under 25, but any sexually active person is at risk. It’s actually really common in both men and women, and can be spread via vaginal, anal, or oral sex. Unfortunately, chlamydia symptoms can be easy to miss.

The STI is sometimes called a silent infection, meaning that most people don’t experience symptoms, according to the CDC. This is especially problematic for women. If chlamydia is left untreated, it can spread to the uterus and fallopian tubes and cause pelvic inflammatory disease. Both PID and untreated chlamydia can cause permanent scarring in the reproductive organs, blocking sperm and eggs from meeting and leading to infertility. In fact, about 25 percent of infertility cases are due to obstructed fallopian tubes, Meike L. Uhler, M.D., a reproductive endocrinology and infertility specialist at the Fertility Centers of Illinois, tells SELF. In some cases, this can be fixed surgically. In others, it cannot be reversed.

Pregnant women with chlamydia are more likely to deliver prematurely, and can pass the infection to their babies, causing eye infection or pneumonia.

The good news is that chlamydia itself is extremely treatable, so if you catch it before it does any damage, you can be completely cured. The key is knowing you even have it, which is tricky because the disease often presents without symptoms—that is why getting tested regularly for STDs is so important. For all other cases, here are the chlamydia symptoms you should look out for.

1. Abnormal vaginal discharge

Lots of things can change how your discharge looks, smells, and feels. A smelly, yellow-green color can be an indication of an infection like chlamydia. (It could be a sign of any other number of infections, though, so again, getting tested is crucial.)

2. A burning sensation when urinating and urgency to urinate

If the infection is in the urethra, it can cause discomfort—either a burning sensation or actual pain—when urinating. You may also feel like you need to go often and that it's urgent. Unfortunately, these are also classic UTI symptoms and can easily be confused for one.

3. Rectal pain, discharge, and/or bleeding.

If you have chlamydia in the rectum, it can cause pain, discharge, and bleeding. If you do have any of these uncomfortable symptoms, you should get checked out ASAP.

4. Lower abdominal pain

Especially if the infection has been left untreated for a while and has caused PID, you may experience lower abdominal pain.

5. Painful sex and bleeding afterward

Chlamydia can cause cervicitis, or inflammation of the cervix, making it extra-sensitive during sexual intercourse. It can also cause bleeding after sex. If the infection spreads and causes PID, that can also make sex less than pleasurable.